Clothes dryer and control therefor



v NOV. 22, 1966 C, A, COBB ETAL 3,286,361

CLOTHES DRYER lAND CONTROL THEREFOR fm IIMIIIIIHIIIII M n-mw, /fZzm f TTORNEYS c:` A. COBB ETAL 3,286,361

CLOTHES DRYER AND CONTROL THEREFOR 4 Sheets-Sheet 2 Nov. 22, 1966` Filed Nov. 12,4 1963 E ZE 4 57 o 44 37 44 81 70 l Il l' l 77 l Je 8 W @1mg/.ZW v' @M7-@MHS Nov- 22, 1966 c. A. COBB ETAL CLOTHES DRYER AND CONTROL THEREFOR Filed `Nov. 12, 1965 4 Sheecs-Sheet 5 w M@ 5 MM 5 MM 0 I fl G l. i fw e g JM 60 Nov. 22, 1966 c;` A. COBB ETAL 3,286,361

CLOTHES DRYER AND CONTROL THEREFOR Filed NOV. 12, 1965 4 Sheets-Sheet 4 ...Ef-3 7 I k I l I @QQ/1m su @WORN/sys United States Patent Oee 3,286,361 Patented Nov. 22, 1966 CLOTHES DRYER AND CONTROL THEREFOR Clifton A. Cobb and William F. Gourdeau, St. Joseph,

Mich., and James T. Williams, Berwyn, Ill., assignors to Whirlpool Corporation, St. Joseph, Mich., a corporation of Delaware Filed Nov. 12, 1963, Ser. No. 322,641 9 Claims. (Cl. 34-31) This invention relates generally to drying systems and dryers and more particularly relates to a method and apparatus for drying materials wherein the thermal energy input rate is automatically adjusted by a sequential control means for a thermostatic control means which regulates the ow volume of air to maintain a predetermined moisture removal rate.

Although the principles of the present invention are of general applicability, a particularly useful embodiment is provided in a drying system of a laundry appliance or dry cleaner wherein a blower is used to drive a stream of temperature conditioned air through a treatment zone. In accordance with prior art procedures, dryer apparatus for clothes, or, for dry cleaning apparatus generally utilizes a single speed blower motor which directs a stream of air through the treatment zone in accordance with a xed flow volume. In accordance with the principles of the present invention, a single speed electric motor is pro vided; however, the blower shaft is particularly characterized by a multiple pulley groove driving hub wherein the multiple grooves are of different diameter and the pulley belt is selectively shiftable between the grooves by means of a motor actuated roller. Thus, the speed of the impeller of the blower and hence the flow volume of the air flowing through the treatment zone is adjusted in a predetermined manner. The motor actuating the roller is placed under the control of a sequential control means or a thermostatic regulating means, thereby to effect control in a fully automatic manner.

It is an object of the present invention to provide a blower apparatus which has a capacity for automatically changing the flow volume of an air stream directed through the treatment zone.

Another object of the present invention is to provide multiple predetermined drying cycles which may be selected at the discretion of the operator.

Yet another object of the present invention is to provide a blower for a dryer wherein the blower shaft has a driving hub characterized by multiple pulley grooves of different diameter and wherein a pulley belt may be selectively shifted between the grooves by motor means such as an electro-mechanical actuator to vary the flow volume of air discharge by the blower.

Yet another object of the present invention is to provide an automated control system which regulates the thermal energy input rate and air flow volume in the treatment chamber of a laundry or dry cleaning apparatus.

Still another object is to provide a drying system in which multiple drying cycles may be selected at the discretion of the operator.

Many other features, advantages and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings in which a preferred structural embodiment of a laundry appliance incorporating the principles of the present invention is shown by way of illustrative example' and in connection with which the methods of the present invention may be effectively practiced.

On the drawings:

FIGURE 1 is a rear view of a dryer, with the rear cover removed, incorporating the principles of the present invention;

FIGURE 2 is an enlarged horizontal fragmentary view of the blower housing with parts removed showing additional details of the pulley belt shifting mechanism and an electro-mechanical actuating means which exemplifies the principles of the present invention;

FIGURE 3 is a partial cross-sectional view of the blower impeller taken generally on line III-III of FIG- URE 1;

FIGURE 4 is a fragmentary top, sectional view of the blower housing showing details of the construction of the belt-shifting means and the electro-mechanical actuator;

FIGURE 5 is a schematic diagram of the control circuit 'of a selective, multiple-speed system dryer utilizing a dual exhaust thermostat operated blower solenoid;

FIGURE 6 is a graphical diagram illustrating the temperature variations in the treatment chamber of a dryer utilizing the control circuit of FIGURE 5 in the automatic mode of operation; and

FIGURE 7 is a schematic diagram of the control circuit of a selective, multiple speed system dryer utilizing a blower solenoid regulated by sequential control means.

As shown on the drawings:

While not specifically limited to the environment of the exemplary dryers herein shown by way of illustration, the principles of the present invention are advantageously incorporated in and practiced with a laundry dryer apparatus shown generally in FIGURE 1 at 10 wherein the machine is shown as having a casing 11 with a console panel 12 in a so-called control tower 13 on one side thereof.

The rear of the machine is shown with a back wall removed, thereby to expose the operating components of the dryer apparatus 10 and as illustrated in FIGURE l, there is provided a single speed electric motor 14. In an exemplary form of dryer construction, the single speed motor can take the form of an electric motor having a normal operating driving speed of 1,725 r.p.m. and has a drive shaft 16 which is attached to a pulley 17 cooperating with a pulley belt shown at 18.

The motor 14 also drives a belt 19 which is trained over the outer periphery of the drum 20. The drum 20 is mounted for rotation on axially disposed shaft 23 so as to extend interior of the casing 11, thereby providing a treatment zone. The shaft 23 is xedly attached to the bulkhead 31. A plurality of ribs 21 and a hub 22, provide stiiening means for a bulkhead 31.

The laundry apparatus 10 incorporates the usual air system through which a stream of Ventilating air is directed. In this connection, the air system includes a conduit 26 having an inlet which may be located at the front lower part of the machine, the conduit 26 extending rearwardly and terminating in a vertical air tempering conduit 27 which is mounted on the bulkhead 31. The conduit 27 has a temperature-conditioned air outlet 26a which leads to the interior of the drum 20. Thermal energy is added to the air stream in air tempering conduit 27 to temperature condition the air which passes through the air inlet 26. A blower shown generally at 30 is located in the air stream and draws temperature-conditioned air from the tempering conduit 27, discharging the stream of temperature-conditioned air through the rear-bulkhead of casing 11 and into the treatment zone for circulation to every section of the rotatable drum used to gently tumble the contents of the drum in warm moving air and without exposing the contents of the drum to direct heat radiation.

An exhaust outlet is als-o provided for the treatment zone in the rear-bulkhead 31 and a vent 32 is shown on the rear of the machine extending through partial back panel 28 which may be connected through a suitable pipe if the machine is vented to the -outside atmosphere or else the discharging air may Vent directly into the space in which the dryer is located.

Although the laundry apparatus is of a type which could be advantageously employed with either a source of heat comprising a gas burning means 35, or an electric resistance element, the present exemplary form of the invention is described for the purposes of illustration in connection with a machine employing a plurality of electrical resistance-type heating elements wherein two separate heating elements 33 and 34 are located within the tempering conduit 27 (see FIGURES 5 and 7). For example, the heating elements 33 nad 34 could comprise elements of 3,600 and 2,000 watts respectively. In accordance with the principles of the present invention, it is contemplated that the volume ow of air `driven to the treatment zone be selectively variable. To effect that end, a speed-changing mechanism is -associated with blower.

In FIGURE 3, there is shown a blower impeller 36 having plural vanes 37 carried on a hub 38 fastened as at 39 to the end of a shaft 40. The shaft is journalled in a bearing sleeve means 41 retained within a bearing housing 42 cushioned in a rubber mount 43 Icarried |by a double wall portion 44 of the rear bulkhead 31 of the casing 11. The bearing housing 42 is formed with a lubricant reservoir 46 preferably filled with a lubricantimpregnated packing material and the reservoir is closed by a closure shown at 47.

On the outside of the rear bulkhead 31 and on the rear of the shaft 40 opposite the impeller 36, there is provided a driving hub 50 retained in co-rotatable assembly with the shaft 40 by means of a set screw 51. The hub 50 is particularly characterized by the formation in the peripheral surface thereof of multiple pulley grooves, for example, 52 and 53, which are of different diameters. The groove 52 has a smaller `diameter than groove 53.

In order to selectively shift the pulley belt 18 between the multiple pulley grooves 52 and 53, a pulley shifting mechanism is provided, different aspects of which are illustrated in FIGURES l, 2, 3, and 4.

Referring to FIGURE 2, the pulley shifting mechanism as indicated generally at 60 and more specifically includes a bracket 61 having a mounting leg 612 secured by fasteners 63 to the outer wall 44 adjacent the hub 50. The bracket includes a second leg 64 which extends at right angles to the leg 62 and carries a pivot fastener 65 through which is connected a rotatable or pivotable disk 66.

The disk 66 has projecting radially outwardly therefrom two yseparate angularly spaced arms or projections 67 and 68. The projection 68 carries a tapered roller 69 in journalled relation and it will be noted from inspection of FIGURE 4 that the projection 68 with the roller 69 thereon is somewhat longer than the corresponding projection 67. The projection -67 has a beltengaging surface 70 on one side thereof and is concavely recessed as at 71 on the lother side thereof, thereby to engage a stop 72 which can be adjustably set by virtue having formed therein an off-center annular opening 73. Stop 72 can -be adjusted by rotation thereof with lever 74 and subsequently secured in place by fastener 75.

Also, projecting radially outwardly from the disk 66 is a lever arm 76 to which is connected a wire linkage 77 and a return spring 78, the opposite end of return spring 78 is secured by means of annular opening to the wall of the rear bulkhead 44 at a point 79 and the opposite end of the wire linkage 77 is secured by means of a loop 80 to a plunger 81 of an electrical solenoid 82 secured to a wall 44 by fasteners 87.

As will be evident from inspecting FIGURE 4, the roll 69 and the projection 67 are angularly disposed to confine in the included angle therebetween the pulley belt 18. Thus, if the disk 66 is pivotally displaced in a clockwise direction the roller 69 will engage the pulley belt 18 and will tend to shift the belt 18 out of the groove 52 and into the groove 53. On the other hand, if the di-sk `66 is rotated in a counterclockwise direction, the

projection 67 will tend to push the pulley belt 18 out of the groove 53 and into the groove `52.

Referring now to FIGURES 5 and 7 the control circuitry for the dryer apparatus 10 is shown as receiving power for the control circuitry via line L1, L2 and N. Lines L1 and L2 are connected to opposite sides of a 200 volt commercial power source and N is connected to the third neutral wire.

In the control circuit of FIGURE 5, there is shown a safety door switch operable upon opening the door to stop the machine if access is desired'before the completion of the drying cycle. A blower speed switch 91 is located on the control tower 13 so as to allow the operator to select a normal position 92, a super position 93, or an automatic position 94.

An inductance element 95 comprising the electromagnetic winding of a solenoid actuating means 82 actuates plunger 81 upon energization, thereby to drive a motion translating means such as wire linkage 77. Associated with the solenoid winding 95 are two pilot light indicators 96 and 96a located in easy viewable location on the control tower 13. The pilot light 96 may be red to indicate high speed yblower operation and the pilot light 96a may be given to indicate slow speed blower operation.

A heater control switch 109 is operated by a timing cam 108 and a single-pole, double-throw center-off switch 110 is operated by a timing cam 107. A thermostat 111 comprising a dual exhaust thermostat is located in a position to sense the temperature of the exhaust air discharged from the treatment chamber 28. An inlet thermostat 112 is located to sense the temperature of the air being introduced into the treatment chamber 28.

In reference to FIGURE 7, the components which correspond to those of FIGURE 5 `are similarly numbered. A single-pole, single-throw blower switch 114 is operated by a timing cam 115 which is rotatably actuated by the timing motor 106.

Prior to starting the dryer, the switch 90 is in the position and the timer cam 108 is exerting sufficient pressure upon a leaf 121 of the switch 109 completing the circuit to contact points shown at 122 and 123. The switch 110 is in a position 124. The dual exhaust thermostat 111 is opener, and the thermostats 104 and 112 are closed. A control knob K of the timing motor 106 located on control tower 13 is set by the operator to the start position for the particular drying cycle desired.

The cycling thermostat 104 is located to sense the temperature of the exhaust from the treatment zone 28. Upon the exhaust reaching a predetermined temperature, the cycling thermostat 104 modulates and reduces the thermal content of the intake air.

An alternative heating method is shown utilizing a gas burner 35 which can be designed to incorporate a cycling thermostat similar to that used in conjunction with the resistive heating elements 33 and 34.

A push-to-start switch 98 .is momentarily closed to start the drying cycle of the dryer 10. The closing of the switch 98 energizes the motor 14 which comprises a starter winding 100, an operating winding 101 and a centrifugal switch contacts 102 and 103. Contact 102 cuts out a starter winding 100 and contact 103 completes the electrical circuit to resistive elements 33 and 34 or, in the alternative system, the gas burner 35 When motor 14 has reached operating speed.

The switch 103 prevents thev lapplication of thermal energy to the dryer until the motor 14 has attained suiiicient rotatable speed. A cycling thermostat 104 which is located to sense the exhaust temperature of the air discharged from treatment chamber 28 effects the decreasing of heat energy in a gradual fashion. This is accomplished since the heating element 33 is continuously in operation while heating element 34 is cycled or modulated. That mode of cycling eliminates the -abrupt changes in the supply of thermal energy to the intake air as in the case with the present heating systems. Thus, gradual, rather than abrupt heating decay is afforded and more efficient operation is attained.

The sequential control means includes a presettable timer motor 106 which is preset by a cycle selector knob K which is located on the control tower 13 for the length of timing cycle desired timed or automatic termination, and is equipped with rotatable operating timing cams 107 and 108. Y

Although the speed changing principles could be advantageously employed with either the timed or automatic terminated cycle, the present exemplary form of the invention is described for the purposes of illustration as used with an automatic cycle termination control.

By means of a selector switch S located on control tower 13 the operator may select either normal speed, super speed or automatic speed shif cycles of operation. The following description will consider each mode of operation in the above order with the sequence of operations in the order `of occurrence.

Normal speed operation When the normal mode of operation is selected, the cycle is accomplished with the blower operating at the lower of the two available speeds. The ope-rator places the switch 91 in the position 92 by selecting the normal speed with the selector switch S. To initiate the drying cycle, the operator depresses the push-to-start switch 98 thus energizing the starting winding 100 and operating the winding 101 of the motor 14. The closing of the switch 98 also actuates the timer motor 106 through the now closed contacts 130-124 and energizes the blower solenoid winding 95 through the switch contact 92 of the switch 91 and energizes green'pilot light 96a which indicates that the belt 18 has been shifted to the pulley 53 driving the blower impeller 36 at normal speed.

As the motor reaches operational speed, the centrifugal switch contact 102 moves to position 126 de-energizing the starting winding 100 and centrifugal switch contacts 103 close completing the circuit to electrical resistive elements 33 and 34 or in a gas heat machine, gas burner 35. After the centrifugal switch contact 1j) moves to 126 the push-to-start switch 98 'may be released without interrupting the operation of the dryer since the circuit is then completed through contacts 102-126.

The timer motor 106 continues in operation for a predetermined time interval, for example ten minutes. At the end of the ten minutes the cam 107 opens the contacts 130-124 thereby de-energizing the timer motor 106. By the time the cam 107 opens the contacts 130-124, the inlet thermostat 112 will have opened due to the heat from the heater elements 33 and 34 or in the gas heated machine the gas heater 35, and subsequently the dual exhaust thermostat which is located on the discharge side of treatment zone 28 will close. As the drying cycle continues, the exhaust temperature is maintained -at an `approximate predetermined level by the cycling of the exhaust thermostat 104 thereby reducing the average rate at which the heat is added to the drying air as the cycle progresses.

Since the dual exhaust thermostat 111 is preset to close at a temperature lower than the opening temperature of the exhaust cycling thermostat 104 in the thermostat 111, it will close before the cycling of the thermostat 104 and remain closed for the remainder of the heating cycle. As the heat input is modulated to a point where the inlet `air has reached the reclosing temperature of the inlet thermostat 112, the thermostat 112 will again close thereby completing the circuit to the time motor 106. The timer in turn operates the leaf 132 of the switch 110 to the position 131 and continues for a predetermined time such as two minutes and the cam 108 opens contacts 121-123 thereby de-energizing the heater elements 33 and 34. The timer motor 106 will continue to run for an additional predetermined period without the heat input thus allowing a cool down period. At the end of the cool down period, the timer cam 108 opens contacts 121-122 thereby terminating the drying cycle of the dryer 10.

Super speed operation When the Super speed mode of operation is selected, the drying cycle is accomplished with the blower operating at the higher of the two available speeds. The operator places the switch 91 in position 93 by selecting the Super speed with the selector switch S. When the switch 91 is in the position 93 the circuit to the blower winding 95 is opened through switch 91 and is placed in a series circuit with the red pilot light 96. Since the solenoid winding 95 is of low resistance and the pilot light 96 is relatively high, the voltage drop will be predominately across the pilot light 96; therefore, energizing the filament of the light 96. The winding 95 will have a very low flow of current insufiicient for the actuation of the solenoid or excessive heating of the winding 95.

The operation of Super speed cycle is identical to the Operation of the above described normal speed cycle except for operation of the blower at the higher (Super) speed, since the speed change solenoid winding 95 will not be energized to shift the belt 18 from the pulley 52.

Automatic speed shift operation When the Automatic" speed shift mode of operation is selected the operation is very similar to the before described cycles except the cycle is accomplished with the blower initially operating at Super speed with an automatic shifting to the lower norma speed when dictated by the sequential timer cam (FIGURE 7) or dual exhaust thermostat 111 (FIGURE 5).

Referring to FIGURE 5 the operator places the switch 91 in the position 94 by selecting the automatic speed with selector switch S. The drying cycle is initiated as explained in the explanation of the operation of the normal and Super speed cycles. The operator depresses the push-to-start switch 98 thus energizing the starting winding 100 and operating the winding 101 of the motor 14. The closing of the switch 98 also actuates the timer motor 106 through now closed contacts 130-124 and energizes the red pilot light 96 which indicates that the blower is operating at the higher speed since the blower speed change solenoid winding 95 is not energized.

As the motor reaches operational speed the centrifugal switch contact 102 moves to position 126 de-energizing the starting winding 100. The centrifugal switch contact 103 closes completing the circuit to the electrical resistive elements 33 and 34 or, in the gas heated machine, the electrically operated gas burner 35. The timer motor 106 continues in operation for a predetermined time interval, for example, ten minutes. At the end of the ten minutes, the timer operated cam 107 opens contacts -124 thereby de-energizing the timer motor 106. The heat from the heating means heater elements 33 and 34 or the gas heating means 35 will cause the inlet thermostat 112 to open before the opening of the timer switch contacts ISO-124. As the materials in the drying zone approach the state of dryness, the evaporation cooling effect is reduced; therefore, the air leaves the drying zone at a higher temperature. When the exhaust temperature reaches the predetermined calibration of the dual exhaust thermostat 111, the thermostat 111 closes completing the circuit to blower speed change solenoid winding 95, thus shifting the blower to the lower speed. The drying operation will continue with the heat input being decreased as determined by the cycling of exhaust thermostat 104 or by a similar means for the gas heated version. As the heated input is modulated to a point where the drying zone inlet air has reached the reclosing temperature of the inlet thermostat 112, the thermostat 112 will reclose thereby completing the circuit to the timer motor 106. The timer continues for a predetermined time, such as two minutes, and the cam 108 opens contacts 121-123,

thereby de-energizing heater elements 33 and 24 or electrically controlled gas heating means 35 in case of the gas heated version. The dryer will continue to operate for an additional predetermined cool down period, for example five minutes, as dictated by the timer without heat input. The blower will continue to operate at the lower speed unless the exhaust temperature falls below the opening temperature of dual exhaust thermostat 111.

If the opening temperature of thermostat 111 is reached, the thermostat 111 will then interrupt the circuit to the blower speed change solenoid winding 95, thus shifting the blower to the higher speed for the remainder of the cool-down cycle. At the end of the cool down the timer cam 108 opens contacts 121-122 thereby terminating the drying cycle of dryer 10.

FIGURE 6 illustrates graphically the operation of the dryer control as described above. Curves 140 and 141 are used in conjunction with the left hand ordinate and curve 142 with the right hand ordinate. The point in time at which the switch 98 is released corresponds to point T1 on the time abscissa.

T-he time the inlet thermostat 112 opens is indicated at the point T2 and the inlet temperature, exhaust temperature and removal rate continue to increase. The point at which the dual exhaust thermostat 111 closes is shown at T3. Thus, energizing the blower solenoid winding 95 results in a slow speed operation of impeller 36. Also, at the point T3, the red pilot light 96 goes out and the green pilot light 96a is energized. The timer 106 continues in operation until the timer cam 107 moves the leaf 132 of the switch 110 to its neutral position 130 stopping the operation of the timer at approximately the crest of the moisture removal rate curve 142. The cycling thermostat 104 is actuated at the point T4 resulting in the cooling down of the inlet temperature as shown by curve 140.

The lowering of the inlet temperature results in the closing of thermostat 112 thus energizing the timer motor 106 which, in turn, operates the leaf 132 of the switch 110 to position 131. The timer cam 108 reduces the pressure on leaf 121 sufficiently to de-energize the heaters 33 and 34 at a point T 5 in preparation for the cooling down period. Between times indicated at points T5 and T6 the treatment chamber is cooled down by impeller 36 drawing unheated air through the materials contained in treatment zone 28. At the point T6, the timer cam 108 terminates the cycle of dryer 10.

FIGURE 7 illustrates a circuit of very similar operation to that of FIGURE 5, except the blower solenoid 95 is controlled by the timer cam 115. The timer cam 115 is constructed to energize the blower solenoid near the end of the drying cycle after the inlet thermostat 112 has reclosed, thus the dryer will operate at the lower blower speed for two minutes with heat input and for the five minutes cool down without heat input.

Although minor modifications might be suggested by those versed in the art, it should be understood that we wish to embody Within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of our contribution to the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The method of drying which includes the steps of (a) driving a blower at a first speed to drive a stream of air through a treatment zone at a corresponding volumetric flow r-ate for effecting a drying action on materials to be dried,

(b) simultaneously adding thermal energy to the air stream ahead of the treatment zone to enhance the drying characteristics of the air stream,

(c) continuing steps (ia) and (b) until the temperature of the air stream leaving the treatment zone attains a predetermined level,

(d) thereafter driving -the blower at a decreased second speed to drive the air stream through the treatment zone at ia correspondingly decreased volumetric flow rate,

(e) subsequent to step (d) stopping the addition of thermal energy to the air stream,

(f) and continuing steps (d) and (e) for a pre-timed cool-down period.

2. A dryer comprising,

means forming a treatment zone in which moisture is removed from materials,

means for directing a stream of air through said treatment zone including a blower,

a first motor for driving said blower,

said blower having a shaft,

a multiple pulley on said shaft ha-ving pulley grooves of different diameter,

a pulley belt on said pulley `and connected to said first motor,

a pulley belt shifting mechanism for selectively shifting said pulley belt from one groove to another,

said pulley Ibelt shifting mechanism comprising a roller,

a lever, a projection, a disk integral with said roller and said lever, a pivot pin pivotally mounting said disk, said pulley belt being confined between said roller and said projection,

and actuating means connected to said lever, whereupon movement of said disk will shift the pulley belt from one groove to another,

said actuating means including a second motor, and circuit means including a sequential control means for regulating the operation of said second motor automatically.

3. A drying apparatus comprising a blower,

a motor,

a speed changing mechanism interconnecting said motor and said blower,

heating means,

and an air system including conduit means and a treatment zone through Which said Iblower directs a stream of air temperature-conditioned by said heating means, circuit control means including a timer,

an inlet thermostat in said air system after said `heating means and said treatment zone,

fa dual exhaust thermostat in said air system downstream of said treatment zone,

and actuating means for regulating said speed changing mechanism,

whereupon said inlet thermostat is responsive to the heat input from said heating means to thereby affect the duration of a programmed cycle,

and said dual exhaust thermostat being responsive to a predetermined exhaust temperature to effect actuation of said speed changing mechanism,

and said speed changing mechanism being actuated to effect a lower blower speed.

4. In a clothes dryer having means defining a treatment zone for receiving wet fabrics to be dried during a drying cycle having first and second drying portions, cornprising:

multiple level heating means for supplying thermal energy to said treatment zone;

thermal control means electrically connected to said multiple level Iheating means,

said thermal control means controlling the level of thermal energy supplied by said multiple level heating means wherein said thermal energy is supplied at a higher level during the first portion of said drying cycle than during said second portion;

Iair translation means including a blower for moving lair through said treatment zone;

transmission means connected to and controlling said air translation means, said transmission means 'having a first lposition driving said blower to move air through said treatment Zone at a iirst volumetric flow rate and a second position driving said blower to move air through said treatment Zone at a second lower volumetric ow rate; and

programming means connected to and controlling said transmission means for operating said blower to move said air through said treatment zone at said rst volumetric flow rate during said first portion of said drying cycle and operating said blower to move air through said treatment zone at said second lower volumetric flow rate during said second portion of said drying cycle.

5. The clothes dryer of claim 4 wherein said programming means includes timer means for controlling the duration of said first and second drying portions of said drying cycle.

6. The clothes dryer of claim 4 wherein said programming means includes a thermally responsive programming switch sensing the temperature of said treatment zone for controlling the duration of said first and second drying portions of said drying cycle in response to the temperature of the air within said treatment zone.

7. The clothes dryer of claim 6 wherein said thermal control means includes thermostatic means sensing the temperature of the air within said treatment zone and cycling said multiple level heating means to vary the level of thermal energy supplied to said treatment zone in response to the tempenature of the air within said treatment zone. i

8. The clothes dryer of claim 4 wherein said transmission means includes a motor for driving said blower,

said blower `having a shaft, a multiple pulley on said shaft having pulley grooves of different diameter, a pulley belt on said pulley and connected to said motor, and a pulley belt shifting mechanism for selectively shifting said pulley belt from one groove to another and thereby changing the speed of said blower. 9. The clothes dryer of claim 8 wherein said programming means includes `a switch controlled by said programming means, and an actuating device connected to said pulley :belt shifting mechanism for effecting shifting of said pulley belt upon actuation of said switch.

References Cited by the Examiner UNITED STATES PATENTS 1,666,917 4/1928 Sargent 34-54 2,369,044 2/ 1945 Hallinan 236-10 2,482,597 9/ 1949 Ritter 230-12 2,887,785 5/1959 Raley 34-45 3,087,351 4/1963 Ross 34-133 X 3,161,481 12/1964 Edwards 34--45 FREDERICK L. MATTESON, IR, Primary Examiner.

WILLIAM F. ODEA, Examiner.

D. A. TArMBURRO, Assistant Examiner. 

1. THE METHOD OF DRYING WHICH INCLUDES THE STEPS OF (A) DRIVING A BLOWER AT A FIRST SPEED TO DRIVE A STREAM OF AIR THROUGH A TREATMENT ZONE AT A CORRESPONDING VOLUMETRIC FLOW RATE FOR EFFECTING A DRYING ACTION ON MATERIALS TO BE DRIED, (B) SIMULTANEOUSLY ADDING THERMAL ENERGY TO THE AIR STREAM AHEAD OF THE TREATMENT ZONE TO ENHANCE THE DRYING CHARACTERISTICS OF THE AIR STREAM, (C) CONTINUING STEPS (A) AND (B) UNTIL THE TEMPERATURE OF THE AIR STREAM LEAVING THE TREATMENT ZONE ATTAINS A PREDETERMINED LEVEL, (D) THEREAFTER DRIVING THE BLOWER AT A DECREASED SECOND SPEED TO DRIVE THE AIR STREAM THROUGH THE TREATMENT ZONE AT A CORRESPONDINGLY DECREASED VOLUMETRIC FLOW RATE, (E) SUBSEQUENT TO STEP (D) STOPPING THE ADDITION OF THERMAL ENERGY TO THE AIR STREAM, (F) AND CONTINUING STEPS (D) AND (E) FOR A PRE-TIMED COOL-DOWN PERIOD. 